1. Field of the Invention
This invention relates to disc apparatuses and, more particularly, to a disc apparatus having a function to discriminate a disc, such as DVD or CD, by irradiating laser light to the disc via an optical pickup.
2. Description of the Prior Art
There is one example of a prior art of this kind as disclosed in a publication of Japanese Patent Laid-open No. 240027/1995 [G11B 7/007, 7/00, 19/12] that was laid open to public on Sep. 12, 1995. This prior art is arranged to discriminate a disc based upon an RF signal level or pattern.
However, there has been a problem that the RF signal, in order to be turned into a read-out signal, cannot be passed through a noise-removing filter and hence is vulnerable to being affected by noise. Meanwhile, if in order to remove such noise an additional circuit must be provided on an RF signal path, there will be deterioration in the RF signal possibly resulting in data error. Thus, in the prior art, erroneous discrimination might occur due to noise.
Therefore, it is a primary object of the present invention to provide a novel disc apparatus with a function to discriminate a disc.
It is another object of the present invention to provide a disc apparatus provided with a novel disc discrimination function that is less affected by noise.
A disc apparatus according to the present invention, comprises: an optical pickup using one main beam and two sub-beams, the optical pickup including a main beam light receiving area to receive the main beam and two sub-beam light receiving areas to respectively receive the two sub-beam; a tracking servo means for receiving an output signal of the two sub-beam light receiving areas and effecting tracking control; a disabling means for disabling the tracking servo means; and an discriminating means for discriminating a disc being loaded using the output signal from the two sub-beam light receiving areas when the tracking servo means is disabled.
A tracking error signal is detected by sub-beams of a three beam method to discriminate a disc according to a level of difference obtained at that time. Specifically, using first and second discs different in track pitch, the sub-beam detecting light receiving elements are positioned for a track pitch of the first disc to detect a tracking error signal. In this case, a similar tracking error signal to the first disc cannot be obtained from the second disc. This is utilized to discriminate the disc.
According to the present invention, there is no possibility of erroneous discrimination due to noise because a tracking signal is used in the discrimination of a disc, such as CD or DVD. That is, the tracking error signal is narrow in band range as compared to the main beam (RF signal). Further, generally a servo filter is inserted in a signal path therefor. It is therefore possible to discriminate a disc in a manner resistive to noise, free from data error and-hence correctly.
The above described objects and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.